Windows live writer is undoubtedly the most popular blogging client for Windows but there are some concerns if your blog is on WordPress. You can’t add custom fields to your posts from Windows live writer by default.
Some bloggers use custom fields in their theme such as showing a thumbnail image or may be showing the post’s meta description as excerpts. In those cases, you can’t directly publish a post from Windows live writer. You have to save the post as draft, login to your blog, add the custom fields and carry on with publishing.
To solve this issue, download this plugin from Windows live writer plugins gallery and paste it in the plugins folder where Windows Live writer is installed. Typically the folder resides in C: > Program Files > Windows Live > Writer > Plugins.
Restart Windows live writer and write a post. When you hit publish, Windows live writer will prompt you with a message as shown below
Hit Yes, and Windows Live writer will prompt you to add custom fields and save the post as draft or publish it in your blog
You can use multiple custom fields in your post using this plugin. A good idea may be to add the meta title, meta description and keywords tag from custom fields and later paste them in All in One seo pack description fields. There are some workarounds for adding All In One SEO Descriptions from Windows Live Writer and managing blog comments.
Note: If you are having Image related issues with Windows Live writer, check out this Image problem troubleshooting guide.