Bool tool brush question After using bool tool,brush boolean difference,
how to make brush object stay for another difference bool?

Now, when I apply brush boolean difference, brush object is gone.
If you make the brush object active after Difference brush was added and apply it only for the brush it will remain undeleted, just its Maximum Draw Type will be set to Bounds (it will return to Textured once Difference brush is removed from the object). However the final effect of the brush will be applied to the canvas.