You can add 2-3 optional assistance exercises like Pull-ups at the end of StrongLifts 5×5. But you don’t need to because StrongLifts 5×5 is a full body training program that works all your muscles already. Holding the bar on every exercise works your arms indirectly. Pulling it on Barbell Row is similar to a curl movement.
If you add assistance at the end of StrongLifts 5×5, remember that, as the name implies, it’s ASSISTANCE. The goal of StrongLifts 5×5 is to boost your Squat, and to boost it quickly, that’s where most of your gains will come from. It’s not making up lack of Squat, lack of wanting to Squat, lack of wanting to Squat heavy, by a half dozen of assistance exercises at the end of your workout.
If you’re short on time, don’t do the assistance exercises. This will keep the length of your workout short. If you have to skip on something, assistance is better than Squat or any other of the main exercises. The majority of your results will come from doing the Squat, Bench Press and Deadlift where you can lift the heaviest weights. Tons of people have achieved bigger arms without doing a single curl or even Pullup. But just by getting their Squat from 0 to 3 plates a side (that’s 140kg or 300lb).
If you want to emphasize, your arms, 2-3 sets of Dips/Chinups at the end of your workout is fine. Dips at the end of Workout A, Chinups at the end of Workout B. Add weight like with any other exercise.But remember your arms will increase in size even if you didn’t do these exercises but just increased your Squat to 3 plates, Bench to 2 plates, Deadlift to 4 plates. Anybody who trains seriously for a year can achieve that. Not hard. You will never meet a 400lb Squatter with skinny arms or weak ab muscles – these are compounds.
Do not get caught up with that “more is better” mentality, and do not believe that nonsense that you can get good at several things at the same time. You need to make choices, sacrifice some exercises so you can prioritize others. A lot of guys try to achieve too many things a time, lose focus, and end up accomplishing nothing. Don’t be one of them. Focus on the heavy compound exercises – increasing your Squat, Bench and Deadlift!