HTTP Sampler/Body data or Files upload tab selections are not remembered

**eR@SeR** ([Bug 65140](https://bz.apache.org/bugzilla//show_bug.cgi?id=65140&redirect=false)):
Hello,

Body data or Files upload tab selections are not remembered in some cases:

1. Add one or more HTTP Samplers, click on Body Data tab (leave it blank)

then click on any other element in tree pane and get back to HTTP sampler

or

right click on current HTTP sampler or any other element in tree pane

or

click on any toolbar button like Toggle, Start, Clear All etc.

Actual:

Body Data tab selection is not remembered. Parameters tab is selected instead.

Expected:

Body data tab selection/state is remembered.

----

2. Add one or more HTTP Samplers, click on Files upload tab (leave it blank or fill one or more files to upload)

then click on any other element in tree pane and get back to HTTP sampler

or

right click on current HTTP sampler or any other element in tree pane

or

click on any toolbar button like Toggle, Start, Clear All etc.

Actual:

Files upload tab selection is not remembered. Parameters tab is selected instead.

Expected:

Files upload tab selection/state is remembered.

----

Currently, it is hard to work if user tests file uploads. User has to switch to Files upload tab every time :/

Jmeter 5.5 acdb648
Microsoft Windows 10 Pro 64-bit
java version "15.0.1" 2020-10-20

Version: Nightly
Severity: normal
OS:

Start by reproducing the issue in the HTTP Sampler using the Body Data and Files upload tabs, then inspect the HTTP Sampler UI entry point that controls those selections. Verify the behavior after selecting another tree element, using a context menu, or pressing a toolbar button. Done means the selected tab or state is restored when returning to the sampler.

Written by the indexing model from the issue text.