ONLINE version (not on-prem) -- if you are using the getdata in powerbi -- the odata source data entities are controlled by Microsoft. product team. you are stating that the data does not include blanks. there is little to no documentation on these. you should probably request an option to include blanks or a workaround to deal with this in a support ticket. another solution would be to have the entire list and do a left outer join which would include the entire list -- the items with data would be populated and the others would be null or zero.
in power query you can transform data from the odata source. and in powerbi report designer develop/format your report.
the blanks lines you want between groups would be done in formatting the power bi report --if that is what you are using.