Parameters are not shown when I create new parameters in sketch

Hello,

 

I can't see my newly created parameters in the "Parameters and Relations" list when I create a new parameter in the sketch, but it's appear in the tree.

I explain my error as below image.

 

As you can see above images, my newly created parameter is appear in the tree, but everything is removed in "Parameters and Relation" windows even though "Length.1" is originally existed but disappeared too.

Please give me answer if you have any solution or reason for this error.

 

Thank you.