v4.61pre3

I really like seeing the word "fixed" in the changelog. A pile of little things make a huge thing. :)

Same here. Seems to work like I showed earlier only with the default theme and the single solo button added to the toolbar. With my regular customized toolbar, it's like your screencap above; Toggle solo action does work but nothing is showing in the toolbar. The filter solo state does read out in tooltip when I hover over the given button, but no highlight/color changes anywhere.

I don't get toolbar_filter_solo.png to show up at all (other than assign it as icon from the toolbar icon folder. I tried adding the solo toggle action to a toolbar button but that doesn't help here. Weirdness about that button: It is always "lit", even when filter solo is disabled (looks like that's the case for xpander, too).

Yep, that's how I did it and how it looks like here too. I added the toggle filter solo action to the toolbar and chose the toolbar_filter_solo.png as the icon. It looks like it is "lit" all the time, but it is actually the filter on/off icon which gets lit up when solo is on. But only with the default theme and no custom toolbar, except the before mentioned action/button. edit: Ok, I got it working like I showed earlier with a custom theme also, but only without my custom MIDI toolbar.

Aha, it works with an uncustomized toolbar indeed :). And only from the theme image folder if all three filter png's are existing (I think). It does not work from data\toolbar_icons folder. EDIT: Actually, the toolbar can be customized, but the filter button's icon has to be default

Well... time to fix those issues then! It definitely HAS to work from customized toolbars AND from Data/toolbar_icons folder! :D

Isn't that why we're reporting here :D I assume "works from data\toolbar_icons" means also "works with customized filter button" ;)