I want to suggest a feature that no doubt many artists would appreciate, as it is a subject that is really not taken into consideration on many programs unfortunately.
When drawing straight lines with SHIFT, it would be great to have the ability to decide how much pressure the pen would have. currently it is always max pressure.
When drawing freehand and then needing to make a straight line, having the line at max pressure makes it not fit the rest of the lines. If you'd want it to fit, you'll have to change brush or edit it every time you make straight lines. If you would be able to set (with a slider for the brush for example) the pressure level for the straight lines, you would be able to set it to for example 70% so that the rest of the lines would match it.
Currently Photoshop has a not very good system of pressure on straight lines, but it's more flowing than clip studio paint that has also max pressure. I really think that would be a fantastic feature on Paintstorm! Making straight lines very intuitive and convenient.
I hope my explanation is clear, thanks!