Seems to work just fine. Just as good as the paid option from Trello.

Would be nice if the collapse icon had a light grey border to aid visibility, as a white circle on light grey list background is not very distinctive.

Using FF v129 (64-bit), the collapse icon does not change orientation to horizontal when list is in collapsed state, as shown in the screenshot.

Just what I was looking for! A couple of warts here and there but this add-on has been overall great.

Great add-on, helped me immensely. I've been using it for about a year. However, I do have a few gripes with it.

when you try to move a collapsed list it clips into the adjacent list when expanded, which requires you to refresh the page to fix it.

Also, when a list is collapsed, when you expand it, for some reason the title of the list gets a huge empty space under it that requires you to click and click again on the title to fix it.

Also I also would love a feature to increase the length of the collapsed list. When the title is long it ends up clipping the options button.

Very convenient! Thanks to the developer!
Minus one star because the toolbar button doesn't do anything for me.

Very simple extension, does exactly what it's supposed to do. Helps keep more boards a bit more organized.

Changes I would suggest is removing the icon from the toolbar as it is unnecessary since it adds no functionality (yes I can just remove it or add it to the overflow menu)
Also if you create a new list you have to leave the board to be able to collapse it