SUMMARY
Most of the proposed currency formats for Switzerland are wrong since they use a decimal comma instead of a decimal point. 

STEPS TO REPRODUCE
1. System Settings > Formats > Numeric, Currency and Time Formats
2. Select e.g. fr_CH (= Western Switzerland, aka Romandie) or de_CH.
3. Observe the number displayed under "Currency"

OBSERVED RESULT
For fr_CH, the currency is shown as "24,00 CHF"
For de_CH, the currency is shown as "CHF 24.00"

EXPECTED RESULT
For fr_CH, the currency should be "24.00 CHF"
For de_CH, the currency should be "Fr. 24.00"

For currency, Switzerland uses a decimal point => Rules 546 and 514 in the PDF at https://www.bk.admin.ch/bk/de/home/dokumentation/sprachen/hilfsmittel-textredaktion/schreibweisungen.html 

SOFTWARE/OS VERSIONS
Debian Buster
KDE Frameworks 5.54.0
Qt 5.11.3 (built against 5.11.3)
The xcb windowing system

ADDITIONAL INFORMATION
The problem could be solved easily if there were a means to (re-)introduce custom formats ... as was the case in previous KDE versions.