How to SNAP top and down menu elements?

[listy]

"Almost all activity when tab is changed is Recalculate style."

Interesting.  This widget could definitely use some css centralization.  It's something I can take a look at.

I don't think the problem with the widgets in the rows, but the count of rows and columns are matter.
You can reproduce slowness if you open table with 400+ rows, and 10+ cols.
When such "heavy" table opened the whole browser tab, and even left sidebar became laggy and stutter.

One way is to avoid big tables, but we have something like Assets in Episode, which showing all assets available, so scriptwriter can scroll them and add needed to his episode