In fact, the best would be to let us define the horizontal scale.

I, too, stumbled upon this.

Obviously it would be nice to have specific features like mentioned above, but I think just to have on par featureset with the former IDE it would be wise to readd display of 500 data points like in the earlier versions. It would be quite odd to have a successor that does not have or has less of a specific feature than the predecessor.
I only noticed this when trying to debug something using the serial plotter and found out that for myself 50 data points were absolutely not adequate for my specific situation.

I tried changing this line
https://github.com/arduino/arduino-serial-plotter-webapp/blob/04a460e0c21609a63c4064f561990c0128c5a0ed/src/ChartPlotter.tsx#L46
in the bundled package that is being fetched/created when building arduino-ide. The build process did not edit the file back to what it was before, however, unfortunately, it did not increase the number of data points.
Being unfamiliar with the build process, I don't know if this is in fact the wrong line of code to adapt, or if the change just doesn't make it into the final arduino-ide build for some reason.

The change in itself would seem to be rather trivial, given that and the featureset of the predecessor I would really like to see the this implemented before the final release.

I'm running rc9.4 on Linux Mint 21 and the plotter frustrates me. With data once per second plotter shows only 5 X-axis data sets no matter how large I make the window. At fast rate such as 100 data sets / second it shows 50. I can't seem to display 500 seat.

Hi all. We really appreciate the feedback about how the Arduino IDE 2.x Serial Plotter can be improved. However, once the message has been received, additional comments that don't add any new information can add up to a lot of notifications for those of us who watch this repository to keep up with the development work.

If you only want to express support then I suggest the use of GitHub's "Reactions" feature.

Discussion is always welcome over on the Arduino Forum:

https://forum.arduino.cc/

Thanks in advance for your cooperation.
Per

The serial plotter is a web application that is installed as part of Arduino IDE since it's running as a web application, bundled source code can be modified on a local machine.

The package can be found in the installation folder of Arduino IDE
\Arduino IDE\resources\app\node_modules\arduino-serial-plotter-webapp\build\static\js\
main.35ae02cb.chunk.js can be modified to change values threshold value, need to replace U=Object(o.useState)(50) with U=Object(o.useState)(5000) it will increase maximum data points to 5000.

Tested with Arduino IDE 2.0.2 version.

I consider the auto scaling of plot width a valuable feature. As it stands now, the plot width auto scales to full width as the data fills to 50 samples, then the plotter becomes a sliding window.

It would be useful to have the plot width auto scale to full width as the data fills to 500 samples (or a user set limit), then the sliding window activates.

Same code, 100 samples shown on plotter using Arduino IDE 1.8.19 ...

A PR for adding a menu to control the number of data points has been submitted to the repository where the Serial Plotter codebase is hosted:

arduino/arduino-serial-plotter-webapp#32

Please refrain from commenting on that PR thread unless you have some significant and unique information to add. If you only want to express your support for the PR or a comment in the thread, use the "Reactions" feature to add a 👍, etc. If the thread becomes a source of notification noise due to the addition of comments that don't add significant and unique information, as happened here, I will be forced to lock the conversation, which might prevent the addition of comments that are actually of value.