If you are checking to see that a replacer's files were added as expected, since many of them do not have plugins, you need to select 'Data files' in order to see that its contents were imported.
In the OMOD creation window, there are two views corresponding to the radio buttons at the bottom of the window. The only time to do otherwise is when you are instructed to add a specific downloaded file for an OMOD installer (probably separate from the mod download) or you modify the OMOD script appropriately for the changes. Feel free to add patches and add-ons into separate OMODs (which can be installed after the "parent" OMOD). The scripts will probably break or the files may simply not be installed at all. Absolutely DO NOT add "extra" files to scripted OMODs. OMOD scripts are very specific to the contents of the OMOD with which they are packaged. Steam users need to have the obse_loader.exe placed in the Oblivion folder in order for many OMOD scripts to recognize that OBSE is installed. Launching Oblivion through OBMM automatically launches the game with OBSE, if OBSE is detected. OBMM has a lot of useful features among its 'Batch actions', 'Import/Export' and 'Utilities' submenus. The default OMODs folder is Oblivion/obmm/mods, and it can be changed via the Settings menu. OBMM has to be installed in Oblivion's install folder. Fortunately, most mods have a simple installation and package format, which means that the only thing to be done in the OMOD creation window after adding the archive is to fill out any relevant information. The examples below are not exhaustive, but they should give some idea of how to deal with various package types. The last group requires a variable amout of work to ready for OMOD installation. The second needs to be added via the OMOD Creation Window's 'Add archive', and then the OMOD can be completed. The first needs to be double-clicked to be loaded into OBMM. In that mindset, mod downloads can quickly be broken into three groups: OMOD, OMOD-Ready, and neither. Once a mod is in OMOD format, it can be activated and deactivated with a double-click. For OBMM users, this means getting every mod packed into an OMOD. Use the same process to address each mod. This simplest mod management approach is to use one tool for one task. 5.2 Do Post-Installation Configurations. 2.2.28 Visually Enchanted Customizer Fixed. 2.2.27 Seph's Hand-to-Hand Animation Replacer. 2.2.18 Gates to Aesgaard Episode 1 (GTA1). 2.2.17 Unofficial Official Mods Patches (UOMP). 2.2.16 Unofficial Shivering Isles Patch (USIP). 2.2.12 Qarl's Texture Pack III Redimized (QTP3R). 2.2 Examine and Convert the Downloaded Archives.