How to change thumbnail size?

[overdriven]

How to change thumbnail size?

When I use my mouse scroll + control it only changes the font size.

It used to be possible when hovering on thumbnails (an arrow would appear in thumbnail's corner) but I don't have this option anymore.

[oMega Support]

Apparently you have unpressed this button (usually located in upper left corner). Press it, the resize corner on the thumbnail should appear.