You can only edit components in such way (see Layer/Display Mode/contrast Edit). Editing traces/copper objects of another layer is not possible (I agree with you when you have 2 layer PCB, but what about 8 signal layers). Swapping between top and bottom is easy - use "W" key. I would also recommend ...

Pad setup button is not necessary - choose Properties tab in the right side and then "Place Pad" tool, same with all other tools (we also plan to extend manual routing and its properties in the next version).

Select all components, right click on one of them > Save to library > Save To File

Seems we fixed this some time ago.
I have tried to make pattern with 4 assymetric polygonal pads (rotated to all angles) and place it into PCB Layout. Seems pads are similar in Pattern Editor and PCB. Could you please check your version of software (see Help/About), then if it is not 2.1.0.7 - try ...

We plan to add different routing modes in the next minor update (will be on the properties panel with the hotkey to change).

It is not necessary to uninstall anything. Pattern editor uses the same palette as PCB Layout, so the way to change palette for patterns is changing it in PCB Layout. When PCB Layout was not used yet and its registry is empty, default white palette is applied.

It is not possible in DipTrace at the moment - trace nodes are always rounded.

I'll have a play with the panelize and see what i can achieve, thanks!

You can use Edit/Panelizing feature of DipTrace + add board cutout shapes with panelizing off (right click on the shape / Do Not Panelize)

See File/Design Information

Currently it is one of the ways to work around. We plan to add rectangular and oval pad holes in the next minor update.