Pigtail off the 40A breaker you already have.
Why? Because this panel is seriously oversubscribed already. Put the A/C and the electric car charger on the same 40A breaker, and don't run them at the same time ever.
This way at least they'll trip the shared 40A right here instead of making you put on pants and shoes and trudge off to wherever your main breaker is. In the dark.
Occasionally, folks ask about automated ways to sense current and disable loads when other loads are high. You could use something like that. Since all your wires go upwards, it wouldn't be hard to group all the branch circuit L1 hots into a bundle, and the L2s likewise.
If I had a Siemens, ya ha...
If you get that big panel, get a Siemens. There's a $20 strap kit that lets you interlock two 2-pole breakers so only one can be on at once. Then you can just make A/C and EV charger mutually exclusive. (the kit is made for generator interlocks, but it'll work fine forward-feeding too.) Of course that gadget takes 4 spaces, so it's a privilege of having a big panel.
Get a handle-tie for breakers 2 and 3 also
I did a quick look. Disregarding the A/C, which doesn't use a neutral, I see 9 hots and only 7 neutrals tapped. Two of your circuits are *multi-wire branch circuits. (MWBC) These need to have their handles tied.
The first pair is #2 and #3, and the other pair is #4 and #5.
If you look at the weird bit of metal on breaker 4, that's what that is. Get another one for breaker 2.
The good news is the MWBCs are correctly positioned so they don't overload the neutral. When you convert to that big panel you want, make sure to land those pairs of wires (2-3 being one pair, 4-5 the other) on 2-pole breakers. This is absolutely essential or you will overload the neutral.