What kind of endorsements and sign offs do you need at this point? Keep them in your paper logbook. Logten pro I think lets someone sign it with their finger for that purpose. Could always annotate it in remarks and put their cfi# in or something. But I don't think Delta is going to ask to see your complex endorsement. Anyone in the 121 world should be beyond needing endorsements. Not like an airline signs your logbook endorsing you to take a checkride or signs it after your checkride. Could also print out a page to get signed and scan it and attach it to the digital logbook. If you are flying GA and get ramp checked the Feds don't ask to see your endorsements to see if you are legal to fly a plane.