How to upload pre-planned MGRS way points to Garmin tactix delta

Just got the garmin Tactic delta saphire. The main reason I got it was as an emergency navigation aid, but I’ve noticed that it seems like the only way to plot MGRS grids is to use the project waypoint feature which is a pain to use as adding grids with the little side buttons is extremely time consuming (for my my case, if I’m going to be using my garmin to navigate sh*t has already gone pretty south and seconds are going to matter). 

is there anyway to type in MGRS grids using your phone and have them saved in the garmin? Or even better, plot a route with mgrs grids using ur phone or laptop then have that saved to garmin?