This happens to me all the time (Windows 10).

No, it didn't didn't. I still encounter this when selecting menus, drawing on the canvas, etc, on Windows 11.

SOLUTION: CLOSE LAPTOP LID: The person who said to close your laptop shut, while using external monitor, thank you, that worked for me.

Problem started with Illustrator 2020. This worked for me: "we fixed it by going to preferences > user interface > turn off SCALE CURSOR PROPORTIONATELY" Thank you to the person who posted!

Apple has come out with a new adapter that fixes this issue. Unfortunately, the product name is the same.

I confirmed that the 60Hz version MODEL A2119 EMC 3279 works fine. The offending Apple dongle is MODEL A1621 EMC 2877.

I have seen this issue on my touchbar Macbook Pro using Apple's USB-C AV Adapter and a Dell monitor with 3840x1600 native resolution. The Apple USB-C AV adapter only supports 30Hz which is pretty bad for good mouse operations, but AI also introduces a lag.

I was able to workaround this issue by purchasing a USB-C dongle that supports 60Hz. This doubled my refresh rate which helped all apps and also appeared to have fixed the issue with AI. The dongle that worked for me was made by Newpower(3-in-1 Type C Hub). Make sure it supports 60Hz.

This was only happening on my second monitor, _while_ photoshop was running. Quitting photoshop or moving illustrator helped.

https://www.amazon.com/gp/product/B07PQ5GZK1/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

I was able to work around this issue by using the above dongle instead of Apple's USB-C AV Multiport adapter. Apple's adapter is restricted to 30Hz for my dell 38" monitor, this dongle can do 60Hz.

None of that explains why the lagginess affected Illustrator, but not other Adobe apps, but I can confirm that this adapter did fix the problem on my machine.

Quitting photoshop (had it open in the background) fixed it for me in Illustrator.

I was having the same problem – in Illustrator and InDesign.

I know this is going to sound completely crazy, but I came across a post suggesting that Photoshop (running in the background) might be causing the cursor drag in the other Adobe programs. I quit Photoshop, and the lag was immediately gone!

So frustrating bc I had tried nearly all of the suggestions below (and in other posts) for weeks. Definitely a bug Adobe needs to address.

Like I said, sounds ridiculous, but try it. Hopefully it solves your problem too!

It is happening to me too!! Adobe XD, Photoshop and Premier are working fine on my second monitor, but when on Illustrator my mouse is slowing down and it is absolutely unbearable. I have a MacBook Pro 2017 running MacOS Mojave version 10.14.2 and my Illustrator is the CC 2019 version 23.0.1.
Everything is up to date. I tried following all the tips from this forum and nothing works!!!
It sucks so bad because I want to work with my second monitor, all the other softwares work so it is definitely a problem with Illustrator. PLEASE FIX IT! It has been more than a year that people have been posting here about it!

we fixed it by going to preferences > user interface > turn off SCALE CURSOR PROPORTIONATELY

Hi,

I was having the same problem and seemed to improve when I turn off the "Scale Cursor Proportionately" option in Preferences > User Interface > UI Scaling

I've been using a samsung 4k monitor for my second monitor for the past 3 years and never had any kind of lagging issues until today. It is an Ai issue... and frankly I cant work with it.

https://www.google.com/search?ei=CWrTW9vxMJH9_wSr1rjIBg&q=how+to+corel+draw&oq=how+to+corel+draw&gs_l=psy-ab.3..0i67j0l5j0i10l2j0l2.3203.3203..7621...0.0..0.106.106.0j1......0....1..gws-wiz.......0i71.rElOVbKMVhI

Had the same issue with the latest macOS 10.14, but this workaround worked for me:

I experienced the issue only with second monitor, MacBook display worked just fine. After I once used display mirroring, problem disappeared - even when I moved back to using the second monitor as a separate desktop.

I now have carpal tunnel from straining to "micro-move" my mouse. I'm thinking about switching to sketch. No issues.

I have the exact same issue. Totally terrible to deal with on a 32in 4k external monitor that is rendered useless and have to go back to the 15in workspace of the MacBook screen to actually get work
done. YEA!!!

am experiencing this too. macbook pro early 2015, macos high sierra, dell p2715q as an external monitor. works fine when i don't have the external monitor, but doing work on a 13 inch is just as frustrating as the slow mouse.

support told me to clear the cache. that didn't work and was told i needed to get new monitor drivers. sucks when there are no monitor drivers.

still no fix.

I had the same issue and just solved with this method.

https://helpx.adobe.com/illustrator/kb/illustrator-and-mac-os-high-sierra.html

Solution: This issue has been fixed in macOS 10.13.4. Upgrade to the latest release of macOS to resolve it.

Workaround 1: Disable GPU Preview

In the application bar, click the GPU Performance icon to display the GPU Performance settings in the Preferences dialog box.
Clear the GPU Performance check box and click OK.
Workaround 2: Change the color mode of the document to CMYK.

Choose File > Document Color Mode > CMYK Color.

Absolutely unacceptable.