URL Bully
A desktop UI for leaning on a web server at the URL level — templated requests, variable substitution and live timing, somewhere between curl and Burp.
URL Bully exists to do the things you would normally script — hammer an endpoint, walk a parameter, replay a request with one header changed — without writing the script. Requests are templated with variable substitution ({{host}}, {{base64()}}, {{useragent}}, {{contentlength}}), a context menu encodes and decodes selections and rewrites headers, and templates switch connection type and method to match what is being tested. Response timing is graphed as you go. It is an Electron app, so Linux, macOS and Windows; Node.js, MIT licensed. Rougher than the command-line tools and still early, but usable.