Hii!!
I study Bunpro like this:
I do not study in order of JLPT etc (as bunpro doesnt let me sort grammar in a deck), but I study grammar according to when I see it / read up on it 
Does anyone else do this? Have you found it harder? I think the sentences used in N1 grammar are harder than the ones in N3 for example but I was wondering if anyone else does this 
Perfect plan
From around the middle of N3 onwards I personally did this. I would use the bookmark tool to mark grammar I had looked up or seen in the wild (I would also periodically just look through all my unlearnt grammar and mark things I thought were easy) and then I’d choose whatever looked easiest whenever I studied. This meant I had a nice bank of stuff to study at all times and could focus on the easy wins, so my retention always remained very very high.
The only caveat is I would warn against doing this until you’ve finished N4, preferably a large chunk of N3 as well, as there is an awful lot of stuff that is just variations on more common/basic patterns at the higher levels. Having a solid intuition for what words mean (e.g., ばかり) will make it far easier to pick up more advanced phrases which use them. As you noticed as well, the example sentences will get harder. You can always bookmark the N1 points you come across and save them for later, but still prioritise them. I personally enjoyed the challenge of the harder sentences though 
I would also agree with what @JamesBunpro has said. If you’re not aiming to do any sort of test, then I’d recommend it even more. If you are aiming to do the JLPT at some point though, I would try to aim to do some of the higher level grammar points independently though, as you may never come across them in immersion.
I usually only add grammar from immersion, when I already got a feel of its meaning from immersion. Adding grammar I just read once or twice would be like adding completely new grammar as the example sentences probably outnumber the times I noticed the grammar point in the wild. Can’t really call that grammar learned through immersion 
I do the same with vocab.
And yeah, sometimes I add some N1 vocab and all the review sentences for it are impossible to parse I just switch to flashcard for that item. That wouldn’t make much sense for grammar, though.
I still add my usual number of vocab and grammar items every day with the learn queue, my immersion items are additional. But since I only add ones I already have a good feeling about, the numbers rarely exeed 5 a day. So my review queue doesn’t blow up. I don’t have a deck for them (too much work and I’m lazy), I just drop them directly into my reviews.
I’ve done that. I clicked the ‘add to reviews’ button, but custom deck does look like a better way to do it.
Thank you all! I’m going to speedrun N4 since there are some grammar points I only kinda know, I think what I’ll do is:
I have no interest in JLPT, just reading. If I run out of mined grammar items I’ll probably do a couple random ones each day