Is the cabin already built? Or are you going to have it built?
I would get a pad of graph paper, and start throwing things out to scale.
You wrote, you want to customize your floor plan, which to me means, that you want to move some walls around. Is this what you want? If so, this is not the place to teach you about structural design. Although I can do that. You’ll need to hire a design professional, somebody with architecture experience, to help you if you’re going to be moving walls.
If you just want to move furniture around, you will still need to draw out your plan to scale, and then draw in the furniture sizes and different arrangements.
You'll need to draw it to scale or hire a space planner. Most designers can do that.
I'm not sure. I am getting a pre-fabricated building- the "deluxe lofted barn" cabin & the size I ordered is 14x60 which they call a tiny house but it doesn't seem that tiny to me. I don't want wasted space & I want everything to be "multi- functional". I think I just need a little inspiration for ideas.
See if these help.
If the measurements of your cabin are 14 x 60, that is 840 sq ft, which, I would agree is not tiny. However, keep in mind that if these are the outside measurements, a percentage of the sq footage will eventually be taken up by walls, cabinets, appliances, and fixtures, which will result in the total useable floor space being less than 840 sq ft.