As title says - ive added to my save and most items i am already sucessfully producing marked as X because they have alternative recipes from other unvisited planets.
For example: tin plate coтsidered by mode as locked behind Foliax, however since that was not a starting planet (Lignumis prevents this) i am able (and actually forced to) to craft it on Nauvis

It should only be the recipes from the unvisited planets that are replaced with crosses. Have you ticked all the planets you've visited in the mod settings? If so, I'm going to need more information to understand what's wrong

Ive visited Lignumis and Nauvis so far - both ticked as visited in settings.
Some items have alternative recipes and in case where one of the recipes is locked behind technology requiring visiting planet i haven't been yet - it's icon is replaced with big red X mark. Yea, thats the whole idea of a mod, but wont it be more logical to mark them when ALL recipes for that item are locked, not ANY of them?

Yes, it is supposed to only mark them with a cross if all recipes for it are from locked planets (or available from the start). It has worked for that sort of thing with my testing - Foliax unlocks quantum processors and other Aquilo things and, having ticked Foliax but not Aquilo, those are no longer replaced with crosses.
I've created a game with just the planets you've mentioned (Lignumis and Foliax) as well as bztin which I assume you're using and obviously this mod. Tin plates aren't replaced with crosses with Lignumis and Nauvis ticked. However, the tin ore is until Gleba or Vulcanus are ticked. This is because there is a recipe to craft it on Gleba (and probably one on Vulcanus I haven't found) so that is technically the first time you're able to make it. It obviously needs to also consider when it's mineable on a surface and treat that as an unlock from that planet too. I'll look into how to add that.

Got an update that fixes tin ore for me. I haven't been able to replicate what you were saying about tin plates being locked behind Foliax. They're not for me. I think I'll need a mod list to be able to tell what's going on. Those 2 planets, their required pre-reqs, bztin and this mod doesn't cause it.

Nice observation about ore! hovewer in my case thare way way more red crosses (like 80-90% of craftable right now items and all of them was exactle items with multiple recipes with at least one ogf them locked). I wanted to make screenshot for you to provide more information however i run into new issue: after reanabling setting for icons (i previosly turned it off along with prefixes and map icons (mod still displays useful list of required planets in recipe tooltip )) now i have no red crosses at all. Even when i started new game.
https://freeimage.host/i/C2Vnbcb
https://freeimage.host/i/C2Vo3V1
edit:after update nothing changed