docs: how to add a missing dependency to langflow desktop (#8942)

* add-package-management-for-lf-desktop

* username

* Apply suggestions from code review

Co-authored-by: April I. Murphy <36110273+aimurphy@users.noreply.github.com>

* combine-oss-dependency-management

---------

Co-authored-by: April I. Murphy <36110273+aimurphy@users.noreply.github.com>

docs/docs/Develop/install-custom-dependencies.md

@@ -5,7 +5,30 @@ slug: /install-custom-dependencies
 
 Langflow provides optional dependency groups and support for custom dependencies to extend Langflow functionality.
 
-## Install optional dependency groups
+## Install custom dependencies in Langflow Desktop {#langflow-desktop}
+
+To add dependencies to Langflow Desktop, add an entry for the package to the application's `requirements.txt` file:
+
+    * On macOS, the file is located at `/Users/USER/.langflow/data/requirements.txt`.
+    * On Windows, the file is located at `C:\Users\USER\AppData\Roaming\com.Langflow\data\requirements.txt`.
+
+Add the dependency and version to `requirements.txt` on separate lines in the format `PACKAGE==VERSION`, such as `docling==2.40.0`.
+
+Restart Langflow Desktop to install the dependencies.
+
+If you need to change or uninstall custom dependencies. edit the `requirements.txt` file, and then restart Langflow Desktop.
+
+## Install custom dependencies in Langflow OSS
+
+To install your own custom dependencies in your Langflow environment, add them with your package manager.
+
+If you're working within a cloned Langflow repository, add dependencies with `uv add` because there is already a `pyproject.toml` file for uv to reference:
+
+```bash
+uv add langflow DEPENDENCY
+```
+
+### Install optional dependency groups
 
 Langflow OSS provides optional dependency groups that extend its functionality.
 
@@ -23,16 +46,6 @@ To install multiple extras, use commas to separate each dependency group:
 uv pip install "langflow[deploy,local,postgresql]"
 ```
 
-## Install custom dependencies
-
-To install your own custom dependencies in your Langflow environment, add them with your package manager.
-
-If you're working within a cloned Langflow repository, add dependencies with `uv add` because there is already a `pyproject.toml` file for uv to reference:
-
-```bash
-uv add langflow DEPENDENCY
-```
-
 ### Use a virtual environment to test custom dependencies
 
 When testing locally, use a virtual environment to isolate your dependencies and prevent conflicts with other Python projects.

docs/docs/Get-Started/get-started-installation.md

@@ -63,6 +63,10 @@ To manage your version of Langflow Desktop, follow these steps:
   3. To apply the change, click **Confirm**.
   Langflow desktop restarts to install and activate the new version.
 
+### Manage dependencies in Langflow Desktop
+
+To manage dependencies in Langflow Desktop, see [Install custom dependencies in Langflow Desktop](/install-custom-dependencies#langflow-desktop).
+
 ## Install and run Langflow with Docker {#install-and-run-langflow-docker}
 
 You can use the [Langflow Docker image](https://hub.docker.com/r/langflowai/langflow) to run Langflow in an isolated environment.

docs/docs/Support/troubleshooting.md

@@ -112,6 +112,12 @@ There are two possible reasons for this error:
 
 * **Version conflict during installation**: Some version conflicts might have occurred during the installation process. To resolve this issue, reinstall Langflow and its dependencies by running `python -m pip install langflow --pre -U --force-reinstall`.
 
+### Package is not installed
+
+In Langflow OSS, you can follow the error message's instructions to install the missing dependency.
+
+To manage dependencies in Langflow Desktop, see [Install custom dependencies in Langflow Desktop](/install-custom-dependencies#langflow-desktop).
+
 ## Langflow upgrade issues
 
 The following issues can occur when upgrading your Langflow version.