Is there an easier way than adding StringConstants^? for simple input values such as database names?

If the string constant is just going to a single parameter on a single service, it might be just as easy to add it as a default parameter. Have no links into the given parameters, right click on it and select "Set input parameter". Repeat to inspect or change the parameter.

The default parameter will come into effect if there is no value flowing into the parameter, so it can easily be overridden. The input will be coloured green to indicate that a default value has been set, red if no input has been provided at all, or black if an input has been connected. (This colour coding is not very friendly for colour blind, but you can also right click and see if "Remove default" is shown in the menu)