Until you posted a screenshot, it was not not clear to me that you were referring to the Transfer Settings presets toolbar. My instructions were for the Transfer options dialog.

If you wanted to change the Default transfer settings permanently, do it in preferences:
https://winscp.net/eng/docs/ui_pref_transfer

See also https://winscp.net/eng/docs/transfer_settings#configure

I'm sorry, but there is no "Custom" option under Transfer Settings, but only Default / Text / Binary / New and updated files only / Exclude directories ("Default" is what shows in the window).
Under that I see Transfer type: Binary. And beneath that a settings gearwheel and Configure.
If I click on the phrase Transfer Settings, nothing happens. I see no button.
I attach a screenshot.

@slowreader: Use "Custom", not "Configure". Or simply click on the "Transfer settings" panel or the button.
See https://winscp.net/eng/docs/ui_copy#transfer_settings

Alas, my upper-case filenames no longer are changed to lower case when uploaded to my website. I understand about using Transfer Settings as instructed here, but dang if it matches what I see on my computer. There's "Transfer Settings" in the second menu line; it's set to "Default"; but when I click on "Configure" there's no such option. I'm using WinSCP 5.19.6 (2022-02-22). Is that what robbed me of the option? Can I revert to an earlier version that matches the instructions I see online? Thanks – Dan

Thank you! Works a charm.

Sure, see Filename modification > Lower case in transfer settings:
https://winscp.net/eng/docs/ui_transfer_custom

I often run into this problem: there are caps in the file name that make an href search for that file invalid. Is there a way to ensure that all transfers from my computer to my website will be entirely lower case? Thank you!