This was a enhancement request from a reddit user, which I think is an interesting idea and will improve the usability. The idea is to auto-activate corresponding tool when user clicks on a preset. For example if a user has move tool active, and he clicks on a brush preset, the brush tool should get automatically selected, If he clicks on a gradient preset the gradient tool should get auto activated, selecting pattern should auto-activate fill tool (possibly with fill pattern enabled) clicking and dragging a symbol from vector library should have shape handling tool selected. etc This will reduce the amount of clicks while using Krita. Right now one has to choose the tool to activate it and also click on preset, clicking on a preset will most probably mean that the user needs to use the preset, so enabling this auto activating behaviour will enable him to use the preset right away in one single click. The reddit post for this request is here https://www.reddit.com/r/krita/comments/6s6daq/change_the_behavior_of_how_a_tools_activates_and/
You'd have to really carefully design the state machine here, since we should only activate the brush tool, if the current tool is not a paint tool or the freehand selection paint tool, and, of course, it's not the brush tool that should be selected, but the previously used paint tool, in almost all the cases. This is really going to take some good thinking and flow-charting.