Is it possible to configure an iOS device to remember credentials for a Wifi SSID but NOT auto-join it? I want to: 


leave Wifi enabled on the device
Make iOS remember the password for SSID A (e.g. Private corporate network)
Make iOS never connect to SSID A silently


This allows the following flow: 


Manually connect to SSID A from the Wifi menu
Upon disconnecting from SSID A, require step 4 prior to re-connecting to SSID A


Example: By default, upon entering the range of SSID A, using the iOS device continues to use either built in cellular or SSID B. After step 4 above and until the end of the day, the device will be on the network. 

For now the workarounds are: 


Switch Wifi off when at work. Failure point: Forget to do it in the morning, leading to use of the network when not intending to. Further cons: consumes LTE bandwidth unnecessarily, and disables Wifi (which would disable e.g. tethering)
Forget SSID A in the menu. Dealbreaking pain point: have to use a clipboard manager or other insecure tools or brain power to restore the password for SSID A when actually required to connect.
There's isn't a great solution but one possible workaround is to set SSID A to use a non routing static IP and just switch it back to DHCP whenever you actually want to use it. Just click the circled i to the right of the network name and click the Static toggle.

You'll need to enter a valid (but non functional) static IP and Subnet Mask (I tested with 10.1.1.1 and 255.0.0.0) or it won't keep the static IP setting. This let's you keep wifi on all the time and never enter your password again.