How do I set an existing template as default in LO 6.0.3.2 under Mint 19?

For some time I have used my own custom template as the default template in LO Writer. I recently updated to Mint 19, including LO very. 6.0.3.2. In Mint 18.3, one set the default template by this procedure:
With LO open, go to File, New, Templates. When the Template Manager opens, double-click to open My Templates. When the individual templates appear, choose which one you want as default (now set to “Normal”), click on it once, and a toolbar containing “set as default” appears (double-clicking just opens a new file based on the template).
In the new setup, this no longer works. When I click on what I want to be the default, no toolbar appears. What is the new procedure?

SETUP
End PC Noise custom AMD Fusion Media PC
AMD A8-3850 2.9GHz quad-core CPU
4GB Kingston PC3 RAM
2 Intel 520 series 120GB SATA III SSD
Dell 24” pivot monitor, normally used in portrait mode
Northgate Omnikey Ultra keyboard
Linux Mint 19 Mate
LibreOffice 64-bit 6.0.3.2
Firefox 62.0
AMD A8-3850 2.9GHz quad-core CPU
4GB Kingston PC3 RAM
2 Intel 520 series 120GB SATA III SSD
Dell 24” pivot monitor, normally used in portrait mode
Northgate Omnikey Ultra keyboard
Linux Mint 19 Mate
LibreOffice 64-bit 6.0.3.2
Firefox 62.0