I have a saved search with a formula hyperlink containing a link to a new advanced intercompany journal entry. What I wanted to do is to set default values on thay AICJE. I tried hardcoding it in the meantime by appending &(fieldID)=internalID. For example, &subsidiary=1. But it does not seem to work, the field is not being populated at all.

show me your formula and the result obtained and what you expect

You can repopulate most main line fields with

&record.<fieldID>=<value>