Allow to use symbols in patterns
Imagine I have a star used in several patterns.
I want to replace it with a donut. I’d have to edit each pattern swatch that uses it and replace each star with a donut (I could have used Global Edit to make it faster, but surprise (no) — it doesn’t work in the pattern mode).
And if we were allowed to use symbols in patterns, I could have select all the instances of the star in a pattern and quickly replace it with a donut symbol, or just change the core symbol instead, making a copy of it to have a backup star.
Instead, Ai either hits you with 'pattern support nothing' warning when you exit a pattern mode, or silently expands your symbols if you drag-ndrop it to Swatches, the classic way.