How to randomise order of survey items in Qualtrics where some items have to appear together?
There is probably a better way of doing this, but you could probably do this using the block feature in Qualtrics. For example, I often do this when I have several multi-item scales. Each scale is a block. You might randomise item order within a block, but you can also randomise the order of blocks.

So you could group questions (e.g., 1 and 1a) into their own block and then randomise blocks.

See here for info: https://www.qualtrics.com/support/survey-platform/survey-module/survey-flow/standard-elements/randomizer/