A few years ago they brought out the 'Active drawing area'. This means there are now two areas for the materials to reside. choosing a material from the TC material database, (the same way you used to do it) puts the material into the active area. To create, rename, etc. a material, you need to go to Options menu - Materials - Edit 'Lightworks' Materials. In the dialog, right click on something (The word material, or a material name), brings up the sub menu
If you just want the material for one drawing you can rename, copy, in the 'active drawing'. (click the + sign against active drawing). if there are any materials used in the drawing they will show up here. You can also copy material from the TC Database and paste them into the active drawing. they are automatically only saved with the drawing.
For materials used in multiple drawings, you need to have them in the TC database (same dialog box as above). anything done here should be available for multiple drawings. (I say 'should' as I've known it to fail).
See Render Manager help file
for right click options, but ignore the first bit of that page.