With regard to indirect buffers mentioned in the accepted answer...

M-x clone-indirect-buffer will create an indirect buffer for the current buffer. The name of the new buffer will have '<2>' added to it (or a greater number if you've already got duplicate buffer names). The new buffer is opened in a new window. You can switch back to a single window using C-x 0 or C-x 1.

With M-x winner-mode you can easily switch between the two locations. C-c <left> / M-x winner-undo and C-c <right> / M-x winner-redo switches between window configurations. In this case the configurations will be positions in the two buffers viewing the one file.

Note: the winner-undo and winner-redo functions work on a list of configurations. If the configuration is changed, e.g. moving point, then the current configuration becomes the head of the list and winner-redo is invalid, in this case winner-undo will bring back the previous position.

For the OP's situation this leads to the following process;

1. Turn on winner mode M-x winner-mode
2. Visit file (filename: File1.txt, buffer name: File1.txt)
3. M-x clone-indirect-buffer (new indirect buffer name: File1.txt<2>)
4. Make current window the only window C-x 1
5. Find first edit location, make changes.
6. Switch to original buffer visiting file, C-x b (default will be original buffer unless a switch to another buffer took place since step 3). This creates a new configuration for winner to switch back to.
7. Find alternative edit location, make changes.

A switch to the previous edit location (windowr configuration) depends on whether a change is made to the window configuration between switches;

• If a change is made switch using C-c <left> / M-x winner-undo.
• If no change is made switches use C-c <left> / M-x winner-undo for back and C-c <right> / M-x winner-redo for forward.

A change is anything other than another winner-undo or winner-redo.

With regard to indirect buffers mentioned in the accepted answer...

M-x clone-indirect-buffer will create an indirect buffer for the current buffer. The name of the new buffer will have '<2>' added to it (or a greater number if you've already got duplicate buffer names). The new buffer is opened in a new window. You can switch back to a single window using C-x 0 or C-x 1.

With M-x winner-mode you can easily switch between the two locations. C-c <left> / M-x winner-undo and C-c <right> / M-x winner-redo switches between window configurations. In this case the configurations will be positions in the two buffers viewing the one file.

Note: the winner-undo and winner-redo functions work on a list of configurations. If the configuration is changed, e.g. moving point, then the current configuration becomes the head of the list and winner-redo is invalid, in this case winner-undo will bring back the previous position.

For the OP's situation this leads to the following process;

1. Turn on winner mode M-x winner-mode
2. Visit file (filename: File1.txt, buffer name: File1.txt)
3. M-x clone-indirect-buffer (new indirect buffer name: File1.txt<2>)
4. Make current window the only window C-x 1
5. Find first edit location, make changes.
6. Switch to original buffer visiting file, C-x b (default will be original buffer unless a switch to another buffer took place since step 3). This creates a new configuration for winner to switch back to.
7. Find alternative edit location, make changes.

A switch to the previous edit location (window configuration) depends on whether a change is made to the window configuration between switches;

• If a change is made switch using C-c <left> / M-x winner-undo.
• If no change is made switch using C-c <left> / M-x winner-undo for back and C-c <right> / M-x winner-redo for forward.

A change is anything other than another winner-undo or winner-redo.