Tabby is another name for plain weave. With all laces you can frame your A and B units with plain weave.
Wherever you have just 1 and 4 threaded you will only have plain weave weaving in that area. All the places where you have
12121 which is an A alternating with 43434 which is a B will be weaving in Lace.
When you treadle the tabby treadles you will have plain weave from selvedge to selvedge. When you treadle the A / B alternating section you will have Lace woven in the areas that are threaded.
There is nothing like ‘proceeding’ forward and then observing what is happening.