Hey there. Sorry to hear you’re both having trouble with this.
Personally I don’t find to too difficult to control (drag left/right for scroll, drag up/down for zoom) with either a mouse or a tablet, but I know that what’s comfortable or intuitive can be pretty subjective. Maybe this is something you can get used to over time, but it’s also good to consider potential accessibility issues.
Like @Grum999 mentioned, it may be possible to add a configuration flag inside the kritarc file. For multiple reasons this isn’t something that will be added to Krita’s UI config menu, the main reason being that we are hoping to release as soon as next week.
In the meantime, another option to easily scroll the timeline is to hold space + click + drag anywhere on the timeline frame table. Of course, the drawback here is needing a keyboard or bound button on your tablet, but you might already have one of those. (Aside from that, please give the zoomable scrollbar another chance to see if this is something that you can get used to over time, or whether more work needs to be done to improve control and accessibility. I will do my best to add a kritarc option before 5.0 launch.)
Emmet