There comes a time when I'm animating a particular scene where I want to make a particular gesture or movement last longer or shorter. However this usually involves having to move all of the little green save digits further back on the timeline one by one, and can make a mess.

Another animation tool (Henry's Animation Tool) mitigated this problem by having this:

https://steamuserimages-a.akamaihd.net/ugc/559833874458088226/E8A3A44877818FFAC73C15271881286687090B35/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

It allows you to speed up or slow down a segment of animation, instead of having to manually move every little green digit further down the timeline. If this tool had an optional overlay on the timeline where you could do something similar, it would really make the tool a lot easier to use and would be a big help for longer scenes.