I noticed that when name of the filter is lengthy , then save button is not shown. Please refer the [screenshot attached.
JIRA version 6.0.6
This issue is actually related to the Pie Chart gadget template, there is nothing to be done from the jira-stattable-searchers side.
As a workaround you may want to maximize the pie chart gadget or using a one column layout or you can change the font size in the navigator when configuring.
this issue is caused by long name in the pie chart gadget velocity template, very long name should be truncated and display full text on hover.