New problem: by the time I learn technique C, I've forgotten how to properly do A. And my transitions from B to C are slow enough it's not a combination anymore.
Yeah, that's all part of the normal process. What helps is when you start to see the commonalities in the techniques and connections between them. For example ...
For technique A I want to have my partner's posture broken down with one of their hands on the floor.
For technique B I want to have my partner's posture broken down with a deep grip in their collar
For technique C I want to have my partner's posture broken down with one of their arms across my centerline
For technique D I also want to have my partner's posture broken down with one of their arms across my centerline
For technique E I also want to have my partner's posture broken down with one of their arms across my centerline
For technique F I want to have my partner's posture broken down and have a strong overhook while I get my body off at an angle
For technique G I also want to have my partner's posture broken down and have a strong overhook while I get my body off at an angle
For technique H I also want to have my partner's posture broken down and have a strong overhook while I get my body off at an angle
For technique I I want to have my partner's posture broken down and have a strong underhook
For technique J I want to have my partner posturing up while I have a cross sleeve control
For technique K I want to have my partner posturing up while I'm sitting up with a frame on their neck
For technique L I also want to have my partner posturing up while I'm sitting up with a frame on their neck
For technique M I want to have my partner posturing up while I'm sitting up with a cross grip on their elbow
etc, etc, etc
Bear in mind, this isn't just a matter of memorizing those setup requirements for each technique. It's more a matter of understanding how and why each position makes your partner more vulnerable to certain attacks and not others, so you start to get an intuition for how the whole process works.
Once you have that sort of understanding, then you can start to put together game plans like so ...
I know that most of my best attacks from guard work when my opponent's posture is broken down ...
But when I just try to pull him down, he posts his hands on my chest and belly to block me doing so ...
So I need to hand fight and clear his posts while I pull him down with my legs ...
As I get his posture broken down, I seem to have my best options if I can get a cross grip on his arm and pull it across my centerline...
But he recognizes the danger there and pulls his arm hard to the outside ...
Which gives me the possibility of getting his arm on the floor or getting an underhook or overhook control ...
But he recognizes the danger of all of those and fights hard to posture back up ...
So I recognize that I can't hold him down and sit up myself as he postures back up, adding extra momentum to make him lean back, thereby setting up several potential techniques ...
But he doesn't like the feel of that, so he pushes me back down ...
Which helps me use his momentum to pull him back down and start the process over again
You'll notice that at no point in this cycle was I trying for any specific technique. (At least in the sense of a sweep or submission - you could argue that all the little elements of hand fighting, adjusting body angles, etc could be classified as techniques in themselves.) All I'm trying to do is get some sort of positional advantage, from which various techniques could potentially flow.
BTW - the examples I gave above are all from full guard, just because I find it a convenient position to illustrate general principles. You can develop an equivalent process for half guard, De La Riva guard, etc.