When creating a map and editing the landscape, decorative grass textures can only get in the way or even not needed at all (e.g. if you are developing a golf simulator). In this case, you need to turn off the visual display of grass. You can do it in the Explorer – Workspace – Terrain tab.
Step-by-step instructions

First of all, you must activate the Explorer panel (if it is not displayed at you). To do this, go to the VIEW tab and click on the Explorer button in the upper left corner. Activate the Properties panel in the same way (if it is not displayed).

Next, in the Explorer panel, expand Workspace and click on Terrain. Then go to the Properties panel and uncheck the Decoration option.

It’s done. You’ve removed the grass in Roblox Studio. You can reap the fruits of your labors.