Removing a single number from a TI-BASIC list takes `O(N)` time where `N` is the size of the list. It's simply not practical. Here is the fastest idiom for removing the `X`th element:

    seq(L₁(A+(A≥X)),A,1,dim(L₁)-1→L₁

As for the indentation, the TI-BASIC interpreter needs to step through one colon at a time, which is relatively fast but not instantaneous. I expect each extra colon to take a TI-84 series calc about 0.1 ms each time through. If you want to maximize speed, get rid of the indentation.

As for other optimizations:

Rather than using `E->dim(L1:Fill(1,L1:cumSum(L1->L1` to generate the list, use

    cumSum(binomcdf(E-1,0→L₁

which has the same effect.

You can prescan for numbers not divisible by 2, etc; try this:

    augment({2},1+2cumSum(binomcdf(int(.5E),0

to generate only the odd numbers.

As a different approach, you can generate prime numbers by adding to, not removing from, a list:

    {2
    For(𝑛,3,E,2)       ;close parenthesis to fix parser bug; step by 2 to catch odd numbers
    If min(fPart(𝑛/L₁
    n→L₁(1+dim(L₁
    End
    L₁

It should be of comparable speed or faster.

As a small tip, use the sequence variable *n* instead of a loop index. It takes as much as 0.5 second less to access (depending on how many other variables are in your VAT).