As with most things it depends on what your manuals say....
Practical wise in audit if your unlucky and it gets pulled there will be lots of questions asked. I suspect most FOI will not be happy with it also SAFA inspectors.
In similar situation I have done a manual load sheet. I have also changed on the load sheet but phoned ops and had them produce a proper loadsheet and leave it in my tray for when I get back so that the document pack that gets filed has a clean correct loadsheet. The one that gets left on the ground never gets touched and generally gets filed for three months then gets binned, never gets looked at unless you crash.
I have had a SAFA inspector get upset because we manually changed the Captains name on the Plog after a last min crew swap. Being British I always assume that if there is nothing to say I can't do something then I can do it. A lot of cultures its the opposite if there is nothing to say you can you can't. After that incident the part A was changed to allow it. I believe another crew got caught by the same SAFA inspector afterwards for the same thing and after a bit of grumping they had to leave it. It was a finding when they pulled me.
There is also something similar with Plogs and changing Alternates and changing the fuel plan. But I think most plog generators now include multiple alternates so you can update the main fuel plan manually. We also have a procedure in part A that we can update via phone from flight planning.
So long story short, if your part A documentation section gives you the ability then you can no problems. If it doesn't then you will get to depart but after that it may give issues. A scribble all over the one you have and produce a manual loadsheet in the cruise for filing is also an option if your company allows manual loadsheets. I am told some don't.