In the URL I think filter name and filter value are case sensitive, are you UsinG the Right CaSe ?

Your URL action in Tableau Desktop the URL should look like:

https://tableau-server.com/#/site/testingsite/views/testreport/Summary?filter%20name=<filter%20name>

You must enclose the field name in angle brackets to get the current value. Your current method is passing the string "filter value" which isn't even a valid choice so that's why it appears in parentheses in the target view.

Ah, I hadn't even thought that you might be using a dashboard action to do this, I was simply thinking of a URL linked from somewhere

Maybe add a screenshot or 3 so we can see what's going on ?

If you're just using a browser then don't use the < > brackets

I quickly looked at an old dashboard on my profile, I can do this :

Tableau Public

or this https://public.tableau.com/profile/chris.mcclellan#!/vizhome/iPhone5Test/Dashboard1?Prices=Current

Tableau Public

but I can't find any other quick examples     

Please post an actual TWBX. Your example URL doesn't make sense. If you're trying to filter on Project Manager, your URL should be inserted into Tableau Desktop as https://tableau-Server.com/#/site/xxxxxx/views/ThisisthereportName/Worksheet?Project%20Manager=<Project%20Manager>.

The angle brackets tell Tableau you are inserting a field variable rather than a string literal.

Once you get that working, consider simplifying your URL to start with "/views" so it will always be relative to whichever site you've published to, no need for the full server and site name. If you're filtering from one view to another view in the same workbook you can further simplify the URL string to begin with the view name, e.g. Worksheet. Though in that case you might want to switch from a URL action to a Filter action.

Thank you for explaining that you are emailing links to your users rather than adding a URL action into a Tableau workbook. Try removing all brackets and escaping the embedded space in the names. You should be able to type Project Manager=Jens Bruckmann in your web browser and it will replace the spaces with %20 characters, e.g.

https://tableau-Server.com/#/site/xxxxxx/views/ThisisthereportName/Worksheet?Project%20Manager=Jens%20Bruckmann

Can you create a new workbook and create some dummy data using exactly the same dimension name and dimension values please ?

It has to work, it does work, we just need to figure out why it doesn't work with your data.

Can you have more than one filter?

https://tableau.company.com/#/site/Security_Trust_Office/views/ShellforScorecard/PolicyBar?Implant Organization =<Implant Organization> Claim = <Claim>

https://tableau.company.com/#/site/Security_Trust_Office/views/ShellforScorecard/PolicyBar?Implant Organization =<Implant Organization> Claim = <Claim>