If we can click on a saved preset with control/shift/ or alt button, it should load the preset, but append it to current (without keeping the order).
So we can create multiple simple presets and mix them in current requests list.

If you have the opportunity to do this also for factorio version 1.0 I will be very happy

I've added it for Factorio 1.0 and 1.1 (1.0 only because it's christmas time, since i normally don't add features for old versions)

Loading presets while holding shift + control will merge the presets without preserving the slot number. If you have gaps in one of the presets it will be preserved. That's what i understood by "appending".
There are a few more ways that merging could be done (e.g. start appending each preset in a new row, so that you still have some sort of sense where a preset starts).
I'm currently working on a new feature that kind of has to do with that (importing all craftable items and order them), so i'll see if i can come up with ways for reorganizing the requests in different ways.

I have asked for 1.0, because 1.1 is still experimental.
I am playing with huge bunch of mods (avg ~200), at least a quarter of them have not been updated yet

work like a charm