I'm installing shower tile with an accent strip. Accent tiles are significantly thinner than the rest of tile. Can I layer several kerdi fabric to build thickness? That is the only material I have on hand. Thanks.

How much thinner? Is the accent pc a mosiac or solid tile?

The way it is usually done is to comb on a layer of thinset with a 1/4x1/4 or v notch trowel. let it set, sand off any bumps and fill in the voids with more thinset. then set the strip over that. This method is good for mosaic strips. If you have solid tile, then you can just back butter them.

We found a way that works for us, you stop your field tile at the lower end of the feature strip and installed a stop at the top end of the feature so you can continue your field tile, than we use a float strip and notch each end, depending on thickness needed for the thin set and fill area needed for feature using the modified float strip as a screed.