I started inputting a (none) for main assessments for the summer term with a note in the comments box with words to the effect of 'this assessment didn't happen due to school closure'. This is quite a fiddly procedure as copying and pasting the above statement into each comment box needs to be done separately for each child, and for each subject.
I also found a way to make (none) appear for assessment data by adding a similar note but not adding a score, but again this is fiddly.
I have emailed Insight inquiring as to whether they are working on either a way to add comments like I suggest above more quickly, or perhaps even if they could add an option to select a 'no assessment taken due to closure' option specifically for this purpose, and therefore a comment not being needed at all.
I think this is important to show on Insight so that in years to come so we can quickly and easily see what was missed by children as they move up through the school.
I'll let you know if this goes anywhere!